title: The gene sml0013 of Synechocystis species strain PCC 6803 encodes for a novel subunit of the NAD(P)H oxidoreductase or complex I that is ubiquitously distributed among Cyanobacteria.
abstract: The NAD(P)H oxidoreductase or complex I (NDH1) complex participates in many processes such as respiration, cyclic electron flow, and inorganic carbon concentration in the cyanobacterial cell. Despite immense progress in our understanding of the structure-function relation of the cyanobacterial NDH1 complex, the subunits catalyzing NAD(P)H docking and oxidation are still missing. The gene sml0013 of Synechocystis 6803 encodes for a small protein of unknown function for which homologs exist in all completely known cyanobacterial genomes. The protein exhibits weak similarities to the NDH-dependent flow6 (NDF6) protein, which was reported from Arabidopsis (Arabidopsis thaliana) chloroplasts as a NDH subunit. An sml0013 inactivation mutant of Synechocystis 6803 was generated and characterized. It showed only weak differences regarding growth and pigmentation in various culture conditions; most remarkably, it exhibited a glucose-sensitive phenotype in the light. The genome-wide expression pattern of the Δsml0013::Km mutant was almost identical to the wild type when grown under high CO2 conditions as well as after shifts to low CO2 conditions. However, measurements of the photosystem I redox kinetic in cells of the Δsml0013::Km mutant revealed differences, such as a decreased capability of cyclic electron flow as well as electron flow into respiration in comparison with the wild type. These results suggest that the Sml0013 protein (named NdhP) represents a novel subunit of the cyanobacterial NDH1 complex, mediating its coupling either to the respiratory or the photosynthetic electron flow.
authors.affiliation: University of Rostock, Institute of Biosciences, Department of Plant Physiology , D-18059 Rostock, Germany.
authors.forename: Doreen
authors.initials: D
authors.lastname: Schwarz
authors.forename: Hendrik
authors.initials: H
authors.lastname: Schubert
authors.forename: Jens
authors.initials: J
authors.lastname: Georg
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Hess
authors.forename: Martin
authors.initials: M
authors.lastname: Hagemann
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D004579:Electron Transport / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008969:Molecular Sequence Data; D009154:Mutation; D019255:NADPH Oxidases / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D045331:Photosystem I Protein Complex / Q000235:genetics* / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D046939:Synechocystis / Q000235:genetics* / Q000378:metabolism; D059467:Transcriptome / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D045331:Photosystem I Protein Complex; D021122:Protein Subunits; D002245:Carbon Dioxide; D019255:NADPH Oxidases